American Cast Iron Pipe Co. (Cover Story).

This ductile iron pipe caster became the first North American plant to install a continuous electric arc furnace (Contiarc), and isgoingto use its 65 MW of power to melt and smelt quality iron for years to come.

Industry firsts are something to behold. A foundry goes out on a limb to install new, unproven technology in its plant and sets a higher level for the rest of the industry to reach.

Beyond the research, planning and testing required to develop new technology and install it in an operation, being a trend setter requires one critical ingredient--GUTS.

Especially when the new technology utilizes a method of melting iron never before performed in the foundry industry.

Especially when the new technology carries an $80 million price tag.

The reward for having those guts? If you are American Cast Iron Pipe Co. (ACIPCO), a 3000-employee (2400 foundry) manufacturer of cast ductile iron pressure pipe, steel pipe, iron fittings and centrifugally cast steel tubing in Birmingham, Alabama, the reward is being named MODERN CASTING's 2002 Foundry of the Year.

Setting the Bar

ACIPCO has set a new level in iron melting for the rest of the global foundry industry to follow. In July 2001, the foundry installed the North American foundry industry's first continuous submerged direct current electric arc (Contiarc) furnace. The 65 megawatt (MW) furnace stands 10 stories tall and more than 30 ft wide, and can melt at a rate of more than 100 tons/hr. Thc key to this furnace's molten iron production is that it can tap, charge and arc continuously and simultaneously. It melts using a single 28-in, electrode. As a result, ACIPCO doesn't have to turn the power off to tap or charge the furnace during melting.

The Contiarc furnace is replacing the foundry's 150 in. diameter, 100 tons/hr cupola as the primary melter. The submerged, continuous nature of the furnace makes it more energy-efficient than the cupola. In addition, ACIPCO is now able to both melt and smelt iron in the same furnace system (producing 80 tons! hr while melting and smelting). The furnace can take low-grade scrap (automobile shreddings), direct reduced iron (DRI) and/or hot briquetted iron (HBI) and combine it with coal and silica rock to produce quality ductile base iron with 3.5% carbon (C) and 2.5% silicon (Si).

Furnace Development

In 1993, based on a forecast for increased cast iron demand, ACIPCO was faced with a challenge. The critical raw materials the foundry requires for its cupola melting--clean steel scrap and coke--were becoming increasingly scarce and, consequently, more expensive. As a result, the foundry needed to develop other sources of raw materials (such as DRI or HBI) and more cost-efficient energy sources if it was going to remain a cost-effective operation.

The price of coke has gone up while the cost of electricity has gone down," said Ronald Kern, assistant superintendent of the melt department. "In addition, we melt steel scrap with high residual elements (ACIPCO operates its own automobile shredding facility). With the continuous recycling of metals, these residual element levels are going to continue to rise in the scrap we melt."

This type of charge material cannot be efficiently melted in a cupola or coreless induction furnace--the obvious choices for today's iron foundries looking to upgrade their melt systems. With this mix of charge material, the melt modernization path led to an electric arc furnace, traditionally the method of melting steel.

ACIPCO turned to Alabama Power Co. and the German firm Mannesmann DEMAG Metallurgy for help.

ACIPCO provided the iron melting experience, DEMAG the electric arc furnace design and Alabama Power the smelting experience. ACIPCO originally considered installing two large traditional electric arc furnaces, but concerns about carbon and silicon recovery rates in the molten iron existed. In addition, the total cost to operate two furnaces producing the required 100 tons/hr of iron was higher than that of a cupola.

A new idea was spawned in a meeting between ACIPCO and Alabama Power. Charles Hendrix of Alabama Power said: "You should melt in a submerged arc furnace, which would smelt silicon at the same time."

The idea was a winner.

Developing the Idea

The first test took place in 1994 in a 0.25 MW submerged arc furnace owned by Elkem Metals Co., Kristiansand, Norway. In 1995, ACIPCO reconfigured one of its traditional steel melting electric arc furnaces into a 1 MW submerged electric arc furnace for iron melting. In 1996, trials were conducted in a 0.25 MW Contiarc furnace at the Institute of Non-ferrous Process Metallurgy in Aachen, Germany. In 1997, ACIPCO, DEMAG and Alabama Power built a 5 MW demonstration furnace capable of melting 7 tons/hr. Buoyed by the success of this test furnace, the foundry began installation of its 65 MW production furnace in April 2000.

On July 15, 2001, the first heat was tapped.

"It was the ultimate team effort to make the Contiarc work," said John Woods, vice president of engineering. "We took the design of the furnace proper from our supplier and had to translate it to what we believe worked best for melting our iron."

The Contiarc furnace is a direct current arc furnace with an annular shaft formed by an outer and inner vessel (Fig. 1). The furnace operates continuously with raw material being charged into the top of the annular shaft. Local irregularities in the scrap descent are registered by a charge level indicator and compensated for by an adjustment in the charging sequence.

According to Woods, the charging system is one of the areas of the furnace design that ACIPCO re-engineered for production.

The furnace is charged automatically (5000 lb/charge) through a hopper system that feeds a conveyor to the top of the furnace, Once the charge reaches the top of the furnace, it is deposited into one of eight hoppers that are positioned in a rotating carousel around the top of the furnace. The computerized charging system works in unison with the computerized furnace control system to determine where within the annular shaft charge is required.

By maintaining a full stack of charge material, the heat content of the furnace gases acts as a pre-heater for the charge material. Due to the volume of gas, stack permeability is not an issue; however, the charge material must be sized properly to prevent bridging in the stack.

According to Woods, a primary obstacle in designing the Contiarc for production was upsizing the furnace from the 5 MW research version to 65 MW. "It was a one-of-a-kind so there was no one to learn from but ourselves and our research furnace, said Woods. "The heart of the furnace--the watercooled inner vessel--had to be developed on-site at ACIPCO after the furnace was built."

The continuous arc melting concept is driven by the central cathode (graphite electrode) inside the inner vessel and the corresponding conductive bottom anode. In a traditional arc furnace, when a charge is added, the electrode rises to the top of the charge. In the continuous arc furnace, the inner vessel keeps the electrode submerged. The central graphite electrode is protected against damage from falling scrap by the inner vessel. Its tip operates at a distance below the bottom of this vessel so that the long direct current arc burns between the electrode and the molten metal bath. The shell is shielded from the radiation of the direct current arc by charge materials.

The completely encapsulated melter ensures a reducing atmosphere in the lower part of the furnace and a slightly oxidizing condition in the shaft to achieve the desired process metallurgy and utilization of gases. In addition, this design results in low losses of oxidized iron or silicon. A baghouse system captures emissions.

According to Woods, the one-of-a-kind statement also applied to powering the furnace. Typically, a direct current power supply for an electric arc Furnace requires a large bank of filters at the substation to guard against harmonic feedback. Working with the Robicon Co., a solution was developed that didn't require filters for the power supply, reducing the project cost.

Benefits of the Continuous Arc

The Contiarc furnace is designed to perform both melting and smelting operations. This provides ACIPCO with the following advantages:

* the ability to melt low-cost and abundant shredded scrap, borings, HBI and/or DRI (thus maintaining tramp element control);

* quartz ([SiO.sub.2]), through gravel used in the construction industry, can be substituted for high cost ferrosilicon as a means of developing the necessary silicon level in the melt. "The silicon recovery rate on this furnace is so close to 100%, it's scary," said Kern;

* coal can be used instead of coke during melting to carburize the base metal and reduce the quartz because the carbon product isn't required for heat generation;

* without the use of coke, the sulfur level of the molten metal is reduced.

"Overall, the Contiarc furnace's chemistry and temperature control are superior to the cupola," said Kern. "There is less slag with the Contiarc than that associated with the cupola. It is a reduction furnace. Many oxides that normally act as slag are reduced back into the metal."

During melting, temperature control in the Contiarc furnace is flexible--it can be adjusted by a simple variation of the current/voltage ratio. This allows the iron to be superheated before tapping.

According to ACIPCO, however, everything with the new Contiarc melting method can't be described as "peaches and cream"--the system does have a downside. In addition to the high price tag of the furnace, ACIPCO's learning curve with both the furnace itself and the molten iron it is producing has been very steep. Every experience is a new one because no one has ever melted iron this way.

In Operation

The furnace shell is stationary and does not tilt. Molten iron can be tapped continuously or intermittently depending upon the production requirements.

To tap the furnace (Fig. 2), a hole is drilled into its base by a tapping drill. Once enough iron has been tapped, a clay ceramic is inserted into the hole with a "mud gun" (which is characterized as a hydraulically operated hypodermic needle) to stop the iron flow.

The Contiarc furnace (as well as the cupola) taps into 60-ton collecting ladles that transfer the molten iron (desulfurized to less than 0.01%) to either a 1300 or 1000-ton holding furnace. From there the iron is transferred to five 12.5-ton coreless electric induction furnaces. To produce the ductile iron, magnesium is immersed in the iron in pressurized ladles. Crane ladles transfer the ductile iron to machine ladles at the centrifugal casting molding lines (See "ACIPCO: Casting Pipe Centrifugally" for more casting production information).

ACIPCO does require a secondary melter to handle large scrap unsuitable for the Contiarc. As of press time, the foundry has not decided if this will be the existing cupola or a new electric arc furnace. Currently, the Contiarc and cupola are melting together during a transition period to ensure a large enough iron supply.

One thing the foundry has decided is that the continuous arc melting process is thus far a success for its operation.

"This is only the debut of the continuous arc furnace," said Kern, "We expect it to be an industry leader in years to come."

American Cast Iron Pipe Co.

Birmingham, Alabama

Metals Cast:        Ductile iron (pipe); gray and ductile iron fittings
                    and centrifugal cast steel tubes (fittings).

Mold Capabilities:  Centrifugal casting (metal mold), green sand
                    and nobake.

Core Capabilities:  Shell and coldbox.

Melt Capabilities:  Continuous electric arc and cupola.

Markets Served:     Pressure pipe and pipe fittings for fresh and sewer
                    water transmission; and steel molds for pipe
                    casting.

Foundry Size:       60 acres under roof (2.6 million sq ft).

Employees:          2400 (foundry).

Year Founded:       1905.

Company Officials:  Van Richey, president and CEO; John Cook, vice
                    president & treasurer; J. M. O'Brien, vice president
                    sales & secretary; John Woods, vice president &
                    chief engineer; F. C. Pausic, vice president & works
                    manager.

For More Information

"Coming Technology for Cast Iron Production," H.A. Edge, Jr., C.R. Kern, W. Reichelt, G. Grund, R. Fuchs and C. Hendrix, Proceedings from the CIATF Technical Forum, June 10-11, GIFA '99, Dusseldorf, Germany (1999).

"Contiarc--A New Scrap Melting Technology," W. Hofmann and W. Reichelt, Proceedings from Metallurgical Processes for the Early 21st Century, September 19-23, San Diego, California (1994).

RELATED ARTICLE: An Employer of Choice

Although ACIPCO is recognized as the largest individual cast iron pipe plant in the world, the firm also has achieved recognition for its human resources policies. Fortune magazine has named ACIPCO one of its "100 Best Companies to Work For" five times. The firm also was recognized in the book, The 100 Best Companies to Work For in America (published in 1993). This recognition is due to benefits the firm provides to its more than 3000 employees, including:

* onsite medical and dental care;

* profit sharing and 401K;

* apprenticeship training;

* suggestion program (with implemented suggestions netting a cash reward);

* employee assistance and wellness programs.

ACIPCO: Casting Pipe Centrifugally

A CIPCO has three plants categorized by the small, medium and large-sized ductile iron pipe each manufactures. Poured in 80-60-20 ductile iron, each piece of pipe is centrifugally cast in 20-ft lengths with diameters from 4-64 in.

During casting, molten iron is fed from a machine ladle (in a process similar to diecasting) to one of the horizontal centrifugal casting machines that rotates to force the metal to the surface of the carbon steel pipe-shaped molds. Either a shell or coldbox core has been set automatically on one end of the mold to form the mating surface for each piece of pipe. Unlike any other casting process, centrifugal casting of pipe results in a casting yield of close to 100% of the metal poured.

During casting, the molds arc water cooled to solidify the pipe. Once solidified, the pipe is automatically extracted from the mold and placed on a lifting system for automatic, in-line heat treatment.

ACIPCO also has a separate green sand and nobake iron and steel foundry for the production of pipe fittings and the carbon steel molds for centrifugally cast pipe.

ACIPCO Named 2002 MODERN CASTING Foundry of the Year

MODERN CASTING selects its Foundry of the Year based on the recipient of the AFS Plant Engineering Committee's (1-D) Plant Engineering Award. The AFS Plant Engineering Award is open to all foundries in the U.S., Canada and Mexico, and judging is performed by members of the 1-D committee.

Past winners of the AFS Plant Engineering Award have included Neenah Foundry Co., Neenah, Wisconsin, GM Saginaw Malleable Iron, Saginaw, Michigan; Waupaca Foundry, Inc., Tell City, Indiana; and Charlotte Pipe & Foundry Co., Charlotte, North Carolina.

Nomination forms for the 2003 AFS Plant Engineering Award are available via the MODERN CASTING website at www.moderncasting.com. The AFS Plant Engineering Award winner will be announced at the 2003 AFS Casting Congress in Milwaukee. MODERN CASTING will then profile this foundry as its Foundry of the Year in the July 2003 issue.